Two useful Gimp features

I frequently use the following two Gimp features:

• Remove empty space around an image: There are two ways to do this.
• With the possibility of manual adjustment: Go to the “Rectangle select tool”, select something, click on “Auto Shrink” in the toolbar. Next invoke “Crop to Selection” in the “Image” menu.
• Automatic: Invoke “Autocrop Image” in the “Image” menu.
• Finding out the best compression ratio: If you save a lossless image format such as PNG to a more compact format such as JPG, you can get a live preview of how the compression affects image quality. Very useful for trying out different settings.